Grinding is an abrasive finishing machining process: a grinding wheel, whose hard grains are bonded together, removes very thin layers of material, in the order of a few hundredths of a millimetre per pass. It delivers very tight dimensions, excellent flatness and a fine surface finish.
It is essential for parts hardened by quenching, which cutting tools can no longer work. Depending on the shape, the choice is a surface grinder (the part is held on a magnetic table), a cylindrical grinder for shafts, an internal grinder for bores, or a centreless machine, where the part rolls between the grinding wheel and a regulating wheel, which is very productive for pins and rollers. Wheels are made of corundum or silicon carbide; cubic boron nitride (CBN) is used for very hard steels and diamond for carbide and ceramic. The part is flooded with coolant continuously to limit heating. Tolerances of a few microns and roughness values in the order of Ra 0.2 to 0.8 µm are routinely achieved.
The classic sequence is to machine the part leaving a grinding allowance of a few tenths of a millimetre, harden it, then grind it to correct the distortion from heat treatment. Grinding is used on precision shafts, slideways, tooling plates and blocks, punches and dies, bushes and locating faces. This finishing step belongs to the CNC machining capability and to inspection and metrology.
In a quote request. Indicate only the surfaces to be ground, with their dimensional and geometric tolerances (flatness, parallelism, cylindricity), the target roughness and the hardness after quenching (in HRC). Specify the sequence with heat and surface treatments, as each can distort the part or change its dimensions; the roughness tool helps you choose the Ra value.